Senator Hanson-Young said Ireland's decision should entice those in Parliament who are currently sitting on the fence.

"I would hope that MPs who were perhaps unsure about the impact of this would be looking at the Irish vote and saying, if Catholic Ireland can get on board marriage equality then of course so should Australia," she said.

No constitutional barriers in Australia, advocate says

Australian Marriage Equality national convener Rodney Croome agreed a referendum was not necessary, because there were "no constitutional barriers to moving forward on marriage equality".

He said he hoped the result in Ireland would have a positive impact on the marriage equality debate in Australia.

Australia is now the only developed, English-speaking country that doesn't allow same-sex couples to marry.

Australian Marriage Equality national convener Rodney Croome

"[It showed] increasing momentum, increasing support in parliament, quashing the old myth that Catholics and other people of faith are against marriage equality," he said.

"There's almost majority support for marriage equality in our federal parliament and our focus will be on persuading Tony Abbott and other coalition members to allow a free vote so that Australia can move forward in the same way that Ireland has.

"Australia is now the only developed, English-speaking country that doesn't allow same-sex couples to marry."

Billy Cantwell, editor of Irish-Australian newspaper the Irish Echo, also believed the vote in Ireland would help Australia's same-sex marriage campaign gain momentum.

He said it will encourage other countries to look at similar laws.

"I think it'll put heat on all democracies that haven't actually adopted legislation in this area to actually have another look at it; I hope it does," he said.

"It seems to be marred in politics in Canberra, whereas if it went to a popular vote I have no doubt that it would be carried here."

Ireland is set to become the 19th country in the world to legalise gay marriage, and the 14th in Europe.

Around 3.2 million people were eligible to vote in Friday's referendum, and the national turnout was relatively high at over 60 per cent.